Coal burning boiler



July 26, 1966 F. A. LOEBEL COAL BURNING BOILER Filed May 28, 1964Frederick CZ.

United States Patent 3,262,429 COAL BURNING BOILER Frederick A. Loebel,Milwaukee, Wis., assignor to Cleaver-Brooks Company, a corporation ofWisconsin Filed May 28, 1964, Ser. No. 370,809 1 Claim. ((21.122-149This invention relates in general to boilers, and more particularly toboilers using a solid fuel, such as coal, or the like.

Coal fired boilers are well known in the art, and are used widely inareas where gas is expensive and relatively scarce. However, heretofore,coal fired boilers have had many disadvantages which have limited theircommercial acceptability. For example, in known types of coal firedboilers, it is conventional for the solid products of combustion,commonly known as ash, to be blown through the heat exchange tubes withthe heated air and then out to exhaust. This type of construction isundesirable, in that it creates a health hazard because of airpollution. Additionally, as the ash passes through the heat exchangetubes, there is a tendency for the ash to settle out of the air How andto eventually build up to a point so asto block the flow of air throughthe heat exchange tubes. Blockage of the heat exchange tubes is a veryserious problem in certain types of boilers, since the small diameter ofcertain heat exchange tubes makes it extremely difiicult to clean thetubes. Accordingly, the general purpose of the present invention is toprovide an improved coal fired boiler which obviates the problemsencountered in the pror art by removing ash from the boiler.

An object of the invention is to provide a coal fired wet back boiler.

Another object of the invention is to provide a coal fired boiler withan ash collection device to prevent the passage of ash through the smalldiameter heat exchange tubes.

A further object of the invention is to provide a coal fired boilerwherein ash may be removed in a simple and inexpensive manner.

Still another object of the invention is to provide a coal fired boilerwith improved means for removing the ash from the coal burning furnace,and with additional novel means for removing the ash from the boileritself.

Other objects and advantages of the invention will hereinafter becomemore fully apparent from the following description of the annexeddrawing, in which:

FIG. 1 is a sectional view taken generally centrally through a preferredembodiment of the invention, with certain parts being broken away forclarity of illustration; and

FIG. 2 is a sectional view taken generally as shown along line 22 ofFIG. 1.

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawing and will herein be described indetail a preferred embodiment of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit theinvention to the embodiment illustrated. The scope of the invention willbe pointed out in the appended claim.

Referring now to the drawing, wherein like reference charactersdesignate like or corresponding parts in both FIG. 1 and FIG. 2, theillustrated boiler includes a base in the form of cross braced skids 11,only one of which is shown. Skids 11 are adapted to support the boilerfrom a floor or other support structure, and a pair of cradle brackets12 are secured to, and project upwardly from skids 11. Cradle brackets12 support the boiler on the base 10 with the boiler being slidable forexpansion and contraction of the boiler lengthwise.

The illustrated embodiment of the boiler includes a generallycylindrical shell 14 having a water inlet (not shown) and a steam or hotwater outlet, also not shown. The illustrated boiler is of the wet backvariety, and the structural details not specifically described hereinare set forth in detail in the pending application of Frederick A.Loebel, Serial No. 310,437, filed September 20, 1963, now Patent No.3,211,134. The wet back boiler includes a rear end wall 15 which may bebolted, hinged, welded, or otherwise secured to the shell 14. A frontwall 16 is provided at the opposite end of the boiler from rear wall 15and may be defined by a hinged door, such as that shown in the abovementioned Loebel application. Front wall 16 is preferably provided atthe end of a cup shaped closure member 13 having a flange which isabutted against.

and secured to an adjacent flange on shell 14.

A rear tube sheet 17 is fixed within shell 14 at a point spacedforwardly from rear wall 15 to define an exhaust chamber or manifold 18.A front tube sheet 19 is fixed in shell 14 at a point spaced inwardlyfrom front wall 16, so as to define a manifold 23 therebetween. Thefunction of manifolds 18 and 20 will hereinafter become more fullyapparent.

The illustrated wet back boiler is of the coal fired variety, andaccordingly a coal inlet is provided at 21 in front wall 16. A suitablecoal hopper 22 is fixed to the front wall 16 in surrounding relationwith inlet 21. A traveling grate conveyor 23 may be positionedinteriorly of front wall 16 adjacent inlet 21 to convey coal from thehopper 22 into a furnace 24. It will be understood, of course, thatstoker 23 is motorized, and that the stoker is mounted in the boiler byany suitable means. While a hopper and traveling grate stoker have beenillustrated as means for conveying coal from outside of the boiler intothe furnace, it should also be understood that other arrangements arecontemplated by the present invention, such as for example, by providinga nozzle in front wall 16 through which suitably pulverized coal may beinjected into the furnace. Suitable ignition means may be provided as at25 on the front wall 16, or the firing means may be placed within thefurnace 24, if desired.

A fan, not shown, is mounted with-in a housing 30 that is secured to theupper portion of front wall 16, and a suitable motor 31 is provided todrive the fan. It will be understood, of course, that an appropriate airinlet is provided in front wall 16 through which the air is drawn intomanifold 20. A suitable cylindrical baffle 32 may be mounted on fronttube sheet 19 in concentric relation with furnace 24 to direct the flowof air past the ignited coals into the furnace 24.

The furnace 24 is an elongate cylindrical member which is supported inthe shell 14 in a manner fully described in the aforementioned Loebelapplication, including T bar 34 and brackets 35. It will be readilyapparent that the boiler portion between tube sheets 17 and 19, andwithin shell 14, defines a liquid receiving chamber 14a. Furnace 24extends substantially from end to end of chamber 14a but is spaced fromrear tube sheet 17, in typical wet back boiler fashion.

A pair of first tubes 40 extend longitudinally within chamber 14a, withthe rear end of each tube being connected by a suitable elbow 41 incommunicating relation with furnace 24. From FIG. 1, it is clear thatthe elbows 41 engage the furnace 24 in the two lower quadrants thereof,so as to facilitate the removal of ash from the furnace. Tubes 40 are oflarge diameter, as for example, ten inches, to obviate the problem ofash becoming clogged therein. A suitable elbow 42 is connected to theforward end of tube 40, so as to direct the flow from tube 40 downwardlytoward a suitable ash collection device indicated generally at 43.

The ash collector 43 includes a collection chamber which is generallyrectangular in cross section, and is 3 defined by side walls 44 and 45which project tangentially downward from shell 14. Collector 43 furtherincludes spaced front and rear walls 46 and 47, and a bottom wall 48. Anash removal opening 49 is provided in rear wall 47 and may be connectedto a pneumatic ash conveying system, or the like, by a suitableconnector 50.

A plurality of second tubes 52 are fixed between tube sheets 17 and 19,and the forward end of tubes 52 communicate with manifold 20 while therearward end of tubes 52 communicate with exhaust chamber 18. As isclear from the drawing, tubes 52 are of small diameter, and would besusceptible of being clogged by ash, were not the major portion of theash removed in collector 43. For purposes of example and not oflimitation, it has been found that tubes 52 having a diameter ofapproximately three inches have functioned extremely satisfactorily withtubes 40 having a dimension of approximately ten inches to give a boilerhaving desirable heat transfer characteristics. It will be readilyappreciated that tubes having a three inch diameter would be extremelydifiicult toclean were they to become clogged with ash. Thus, theremoval of the ash by collector 43 provides an efficient, substantiallymaintenance free boiler. An exhaust opening 53 is provided in the uppersurface of shell 14, and a suitable exhaust stack 54 is mounted inopenings 53, and communicates with exhaust chamber 18 to convey the hotgases passing from tubes 52 to atmosphere.

In operation, the coal is inserted into the boiler from hopper 22through inlet 21 where it is ignited and conveyed by stoker 23 into thefurnace 24. Air flowing into the boiler from the fan within housing 30is directed over the burning coals, and into the furnace 24, as shown bythe directional arrows 59. The solid products of combustion will becomeentrained with the heated air, and together they will complete a firstpass through the liquid chamber from front to rear of the furnace 24, asshown by the directional arrows 60. As the heated air and entrained ashmake a first pass through the chamber 14a, a predetermined amount ofheat is given up to the water W, or other liquid, within the chamber.The heated air and entrained ash make a second pass through the chamber14a from rear to front of tubes 40, as shown by the directional arrows61. Since the connection of tubes 40 to furnace 24 by elbows 41 is atthe lower portion of the furnace, the ash will not collect excessivelywithin the furnace. As the heated air and ash pass outwardly from elbow42, the ash will settle in the collector 43, as shown by the directionalarrows 63. The heated air will flow upwardly and toward the tubes 52 bythe force of the fan within housing 30, as shown by the directionalarrows 62. The heated air, substantially free of any ash, will then beconveyed in a third pass from front to rear of tubes 52, as indicated bythe directional arrows 64, and thence into l exhaust chamber 18 and outof the exhaust stack 54 to atmosphere.

I claim:

A solid fuel boiler for heating a liquid medium comprising: a shellhaving a front and a rear end; a rear tube sheet fixed in said shell andspaced from said rear end to define an exhaust chamber between said reartube sheet and said rear end; an exhaust outlet communicating with saidexhaust chamber; a front tube sheet fixed in said shell and spaced fromsaid front end to define a manifold between said front tube sheet andsaid front end; the shell portion between said front and rear tubesheets defining a liquid chamber for receiving the liquid to be heated;an ash collection chamber at the lower portion of said manifold; a solidfuel inlet at the front end of said shell; a furnace within said liquidchamber and having front and rear ends; means for conveying said solidfuel from said inlet into said furnace through said furnace front end;means for igniting said fuel; means for blowing air across the ignitedfuel and into said furnace so that the heated air and solid residue fromthe burned fuel entrained therewith make a first pass through saidliquid chamber from front to rear of said furnace; a pair of largediameter first tubes having front and rear ends, the rear ends of saidfirst tubes communicating with the lower portion of said furnaceadjacent the rear end thereof and extending through said liquid chamberand said front tube sheet into said manifold above said collectionchanber, the front ends of said first tubes being bent downwardly towardsaid collection chamber, so that the heated air and solid residueentrained therewith make a second pass through said liquid chamber fromrear to front of said first tubes with the front end of said first tubesdepositing the solid residue in said ash collector; and a plurality ofsmall diameter second tubes in said liquid chamber, said second tubeseach having a front end communicating with said manifold and -a rear endcommunicating with said exhaust chamber, so that the heated air withoutthe solid residue makes a third pass through said liquid chamber fromfront to rear of said second tubes and into said exhaust chamber and outof said shell through said exhaust outlet.

References Cited by the Examiner UNITED STATES PATENTS 1,974,288 9/1934Nigh 122-149 2,718,881 9/1955 Miller 122149 X FOREIGN PATENTS 226,493 1/1960 Australia. 856,751 12/ 1960 Great Britain.

CHARLES J. MYHRE, Primary Examiner.

FREDERICK L. MATTESON, JR., Assistant Examiner.

